This invention relates to a device for assembly a push V-belt for a continuously variable automatic transmission, in particular for motor vehicles.
Continuously variable transmission, also called CVT, have a first beveled pulley pair upon a drive shaft and a second beveled pulley pair upon an output shaft. Each beveled pulley pair consists of one first stationary pulley in the axial direction and one second beveled movable pulley in axial direction also called primary and secondary pulley. Between the pairs of beveled pulleys extends an endless drive chain called a push V-belt. The primary and secondary pulleys are adjusted by a pressure medium. To this end, via electromagnetic actuators and hydraulic valves, an electronic control unit controls the pressure level of the adjustment spaces of primary and secondary pulleys.
One example of a continuously variable automatic transmission, having a push V-belt, is described in the Applicant""s DE-A 197 34 839. The automatic transmission has a multi-disk clutch and a push V-belt guided upon a pulley set firmly connected with a primary shaft wherein the multi-disk clutch is a disk set with inner disks and outer disks and wherein the inner disks are guided in an inner disk carrier and the outer disks in an outer disk carrier and wherein the disk set can be compressed by one piston. The adjustment of diameter of the corresponding beveled pulleys and the pressurizing of a starting clutch results by means of hydraulic actuating cylinders; the pressures prevailing therein are adjusted by a hydraulic control unit which provides that the push V-belt is prestressed according to the existing engine torque in a manner such that a reliable force transmission occurs without slipping of the push V-belt.
One example of a push V-belt for such CVT transmissions is described in DE-B 42 30 606. This known push V-belt consists of light, long, thick bolts and bearings with smooth cylindrical surfaces and wedge-shaped abrasion-resistant side surfaces with flattened medium edge surfaces made of plastic reinforced with glass fiber of great compressible resistance or of steel tubing with side wedge bodies of plastic, the same as of two wide, outer, flexible, plastic belts reinforced with glass fiber having high tensile strength and of two inner, wide, elastic, thin steel belts. Due to the multiplicity of plastic parts the known push V-belt is still subject to relatively great wear.
Therefore, there are used for powerful engines push V-belts consisting of a plurality of individual metal elements which are assembled and each held upon both sides of the radial plane of the finished push V-belt by an elastically deformable ring set. The ring sets can be made of fine steel and each advantageously has twelve rings disposed concentrically to each other. A push V-belt for one of the CVT transmissions manufactured by the Applicant consists of about 380 elements and of two ring sets each comprising twelve rings.
Until now it has been customary to manually plug the individual elements on one of the ring sets and then, likewise, to manually insert the second ring set in the corresponding groove resulting from the shape of the individual elements.
Especially during the test assembly, the individual elements and the rings of the ring sets are measured for new assemblies, intermediate inspections and final inspections so that the push V-belts has to be disassembled. The assembly and disassembly of the ring sets require the greatest care and highest possible cleanliness in order to keep from damaging the rings of the ring sets. A scratch or even a flaw practically represents a preset breaking point which can later result in failure during use of the transmission.
The problem on which this invention is based is to provide a device for assembly of a push V-belt for a continuously variable transmission with which damage to the rings can be prevented with certainty and with which the assembly of the push V-belt can be carried out considerably quickly.
According to the invention, it is proposed that the device has a circular retaining pulley for centering the first ring set and for lodging the push elements, the same as a ring superposable upon the placed push element and having its inner outline adapted to the outer outline of the push elements so that a force directed radially toward the axis through the central point of the circle formed by the placed push elements acts upon the push elements so that the second ring set can be inserted without action of force in the groove available in the push V-belt.
Damage to the individual rings of the ring set, due to scratch or flaws, is thus eliminated, since by adequate dimensioning of the superposable ring the take-up groove for the ring set corresponds exactly to the circular diameter of the ring set in unloaded state. By exerting light manual force upon the superposed ring, all push elements are simultaneously pressed inwardly within the force acting upon the first lower ring set and so that the second upper ring set can be inserted almost by itself in the groove available in the push V-belt.